1. Field of the Invention
The invention relates to animal watering valves and, more particularly, relates to animal actuated valves for use by mice, ram, and other relatively small laboratory animals or commercially raised animals.
2. Discussion of the Related Art
Animal actuated watering valves are well known. One such valve is disclosed in U.S. Pat. No. 5,065,700 which issued to Cross on Nov. 19, 1991 (the Cross patent). The valve disclosed in the Cross patent employs a housing having an inlet and an outlet connected by an elongated longitudinal bore, a valve element located adjacent the inlet, and an elongated actuating lever or valve stem which extends through the bore, which projects out of the outlet, and which; when deflected by an animal, opens the valve element to permit the passage of fluid through the valve housing. A movable shield or shutter member is provided adjacent the outlet to inhibit the animal from stuffing bedding material or other debris into the outlet and thus inhibits the valve from being unintentionally lodged in its open position.
The watering valve disclosed by the Cross patent suffers from several drawbacks and disadvantages. For instance, neither the shield nor the valve element applies sufficient biasing forces to the valve stem to return the valve stem to its position of rest. A return member in the form of a helical spring must therefore be provided to close the valve when the animal releases the stem. This spring unduly increases the complexity of the valve and is itself subject to corrosion and breakage which could render the valve inoperable. Moreover, the configuration of the helical spring and its relationship to the remainder of the valve prevents adjustment of the valve for varying flow rates.
In addition, the shutter or shield is rigid and thus must move with the stem or actuating lever to permit valve opening. This shield is thus subject to corrosion and jamming which may inhibit or even prevent valve opening or which may cause the valve to stick in its open position.
Some of the problems associated with the valve disclosed by the Cross patent can be alleviated by employing a valve in which the return forces for the valve stem are supplied by an elastomeric diaphragm rather than a return spring. For instance, U.S. Pat. No. 4,258,666 to Edstrom (the Edstrom patent) discloses a valve employing a housing which includes a valve cap in a valve seat and which has an inlet and an outlet connected by an elongated longitudinal bore. An elongated stem extends downstream through the bore from the valve seat, and an elastomeric diaphragm is clamped between the valve cap and the valve seat and acts as a return element for the valve stem. A cone rests upon an upstream surface of the diaphragm and is independently movable relative to the diaphragm. The thus configured valve is operable, upon deflection of a tail of the valve stem by an animal, to permit fluid to flow through the valve at a rate determined by the thickness of a gap formed between the cone and an adjacent surface of the valve cap. This flow rate can be adjusted by adjusting the axial position of the valve cap on the valve seat, thereby adjusting the amount of bulge of the diaphragm on which the cone rests and thus adjusting the position of the cone relative to the valve cap. The diaphragm and associated elements provide sufficient return forces to the valve stem to obviate the need for a separate helical compression spring of the type employed by the device disclosed in the Cross patent.
The Edstrom patent, though eliminating some of the problems associated with the Cross patent, suffers from drawbacks and disadvantages. For instance, the central web portion of the diaphragm is bulged or distorted prior to use and thus cannot be stretched freely. The closing forces of this diaphragm are thus difficult to control. Moreover, the head of the valve stem is flat and thus requires relatively high actuating forces because a mechanical advantage L/W (where L is the length of the valve stem and W is the width of the effective line of contact between the head of the valve stem and the seat) is relatively small because W is relatively large. Finally, the relationship between the diaphragm and the head of the valve stem do not adequately assure centering of the valve stem on the diaphragm. This is important because, if the stem is not centered on the diaphragm, the stroke of the stem will vary depending upon the direction of stem actuation, thus varying the rate of fluid flow through the valve.
Still another animal watering valve is disclosed in co-pending application Ser. No. 08/075,223 to Edstrom et al. (the Edstrom et al. application) Now U. S. Pat. No. 5,337,696. The valve disclosed in the Edstrom et al. application also employs a diaphragm and a valve stem, and additionally employs mechanism to promote valve stem centering on the diaphragm at the cost of forfeiting the adjustability feature discussed above in connection with the Edstrom patent. This valve, like that disclosed in the Edstrom patent, also employs a resilient elastomeric shield at the distal end of the valve which corresponds to the shield of the Cross patent but which is not subject to the corrosion and sticking problems discussed above with respect to the Cross patent. However, due to the arrangement of the shield, water may flow through spaces in the valve where contamination can accumulate.